The present invention relates to electrical connectors, and more particularly to electrical connectors used to interconnect electronic subassemblies, for example printed circuit boards, which are required to be mounted adjacent to each other often in a vertically stacked configuration.
Prior art methods are known for interconnecting electronic assemblies, particularly circuit boards. For example, it is well known to hard wire the boards together, or to use edge connectors carried by the boards which engage with complimentary fixed edge connectors carried within a frame in which the boards are mounted.
A concern with conventional board-to-board connectors is the limited space for connection of the boards or assemblies within the electronic device. With conventional connectors utilizing a plurality of terminals laterally arranged at intervals in a housing, one contact leg of each terminal is soldered to the circuit pattern of one printed board and the other leg of the contact is soldered to the circuit pattern on the other printed board. As a result of the narrow intervals between the terminals and vertical distance between the boards, it is extremely difficult to solder each of the terminals without bridging an adjacent terminal with solder. The soldering procedure is a time consuming and difficult task.
One suggested improvement is disclosed in the European patent specification Publication No. 0 463 487 published on Jan. 2, 1992. Therein, an electrical connector is described having a terminal housing with a plurality of terminals laterally arranged and fixed at regular intervals with two leg contacts of each terminal extending from the housing. A connector casing loosely accommodates the terminal housing and permits the terminal housing to slide up and down within the casing. The casing in turn has extensions for fixing it to one printed board and means to permit the printed board to come into contact with the other terminals. This device, however, requires an adequate space between the circuit boards to accommodate the connector casing and terminal housing. The minimum distance or height between adjacent circuit boards is thus unnecessarily limited, particularly in a stacked configuration of circuit boards.
The published PCT Application No. WO 97/02631 discloses an electrical connector for connecting adjacent circuit boards, including stacked circuit boards. The connector includes a generally I-shaped insulating body defining a plurality of adjacent recesses into which identical contact elements are mounted. The contact elements have at least one resilient contact arm that resiliently bends or moves within the body recess.
U.S. Pat. No. 5,041,016 and the European Patent Specification No. 0 346 206 disclose other types of printed circuit board connectors.
It is a principal object of the present invention to provide an improved electrical connector particularly suited for interconnecting stacked circuit boards.
Still a further object of the present invention is to provide an electrical connector having a relatively minimum height so as to interconnect vertically stacked circuit boards with a minimal separation distance therebetween.
Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In accordance with the objects and purposes of the invention, a low or xe2x80x9cthinxe2x80x9d profile electrical connector assembly is provided for interconnecting physically distinct circuit boards, particularly in a stacked configuration. The electrical connector includes at least one insulating body member having opposite ends and at least one longitudinally extending leg defined between the ends. It should be appreciated that a plurality of such legs may be provided. A plurality of adjacently disposed and spaced apart connector elements are disposed on each of the legs transverse to the longitudinal direction. Preferably, the connectors are disposed at distinct connector positions defined along the leg. For example, the connector positions may be grooves or recesses that are defined at least partly around a circumference of the leg. The grooves or recesses may further comprise engaging or positioning surfaces defined therein that are configured to retain and position each connector element at each connector position along the leg member.
The connector elements are generally open-ended or U-shaped and have a closed end and an open end defined by opposite arm members. The closed ends wrap around the leg at each connector position. Each connector element also includes an outwardly facing contact surface defined on each of the extending arms. In this manner, the connector is disposed between stacked circuit boards with the arms being in mating contact with respective pads of separate facing circuit boards.
Preferably, at least one of the arms of the connectors is an angled resilient arm disposed for pressing mating contact with a respective pad of one of the circuit boards. In this embodiment, the other connector arm may comprise a generally rigid arm that is disposed adjacent to an outer surface of the leg. Thus, the rigid arm may be soldered to its respective circuit board pad with the resilient arm being maintained in pressing contact with its respective pad without soldering. Alternatively, the resilient arm could also be soldered to its respective pad.
The resilient arm may be angled away from the leg and is preferably not in contact with the leg. The resilient arm does not derive its resiliency from being folded back onto the leg as this would limit the minimal height of the assembly due to additional bends in the connector elements. The resilient arm may also have a length so as to extend past, and even over, the longitudinal edge of the leg, for example within the groove or recess defined in the leg. It is preferred that the connector arms do not come into contact with each other.
In an alternative preferred embodiment, both of the connector arms may be resilient arm members disposed for pressing mating contact with respective pads of facing circuit boards. In this embodiment, the arms may move into grooves or recesses defined in the leg of the insulating body upon being pressed against mating pads of the facing circuit boards. The resilient arms may have a length so as to extend over the leg without contacting each other when in the pressed mating configuration to further limit the thickness or profile of the connector.
The connector may also include alignment structure defined on at least one of the ends of the insulating body. The alignment structure can comprise any manner of configuration so as to engage with complimenting structure on the circuit boards to precisely position the connector relative to the circuit boards. For example, the alignment structure may comprise one of a male or female member for engagement with a respective female or male member on the circuit board.
A principal concern of the present invention is to provide a connector having a minimal height or profile. In this regard, a preferred embodiment of the connector comprises a height or profile of less than about 1.0 mm between the opposite arms of the connector elements when the connector is in mating contact between facing circuit boards, and preferably between about 0.5 mm and 0.7 mm. The profile height of the connector is not, however, a limitation of the invention.
In order to aid in precise positioning of the connector element on the circuit boards, engaging structures, such as male or female members, may be defined on the body member so that a positioning cap or similar device may be used to grasp and precisely locate the connector element on a circuit board. This structure may also serve as positioning or alignment structure matable with complimenting structure on the circuit boards.
It should be appreciated that a plurality of connector assemblies according to the invention can be utilized in any number of configurations. For example, a plurality of the connector assemblies could be placed on a single placement cap for placement in any desired pattern on a circuit board.
The present connector assembly is not limited by any particular material of construction and, in this regard, any conventional suitable materials may be utilized in manufacture of the connector assembly components.
The invention will be described in greater detail below through preferred embodiments as illustrated in the attached figures.